Probability Of Failure-free Operation Research Articles

Method of reliability control of thermoelectric systems to ensure thermal regimes

The paper presents the results of research of controllability of the thermoelectric system for ensuring thermal modes of electronic equipment, including a regulator, a cooler, and a component of excess heat removal to the environment. It is shown that for the use of methods of optimization of automatic control systems it is necessary to study the transfer and dynamic characteristics of the object - thermoelectric cooling device with one input and one output. The mathematical model of the thermoelectric cooler of the system of providing thermal modes of a given design is presented, which takes into account the influence of the conditions of interaction of the heat sink with the medium on the main significant parameters, reliability indicators, dynamic and energy characteristics of the single stage cooler. The model is created for the operating range of cooling, level of thermal load, geometry of thermocouple branches, different temperature of the medium, for the characteristic thermal regime of maximum cooling capacity. The results of calculations of the main significant parameters, reliability indicators, dynamic and energy characteristics of the cooler for different medium temperature in the operating temperature range and variation of conditions of heat exchange of the heat sink with the medium are given. It is shown that as the intensity of heat exchange of the heat sink with the medium increases, the temperature difference between the heat sink and the medium decreases. This makes it possible to significantly reduce the relative failure rate, increase the probability of failure-free operation of the thermoelectric cooler and control the reliability indicators of the device of a given design during operation.

10.52209/1609-1825_2024_1_281

A mathematical model for analyzing the parameters of the technical condition of construction objects is developed, on the basis of which, taking into account the wear and tear of damages and defects, the reliability (safety) of the load-bearing structures examined in the process of monitoring was assessed by categories of their serviceability (serviceable, limited serviceable, pre-disaster). On the basis of the calculated initial probabilities of failure-free operation (FRO) at each of the three stages of the technical state on the basis of graph theory the matrices of transient probabilities at different terms of operation of buildings are calculated. This, in turn, allows us to calculate the corresponding reliability indicators: wear rate, mean time to first failure, etc. Based on the processing of statistical data of floor slab inspection, a graph of the dependence of the FRO on the building operation time was obtained, on the basis of which the forecast of the service life (resource) of the studied structures was realized

ФОРМИРОВАНИЕ АЛГОРИТМА НОРМИРОВАНИЯ ПОКАЗАТЕЛЕЙ НАДЕЖНОСТИ ТЕХНИЧЕСКИХ СИСТЕМ

Based on the analysis of the main factors influencing the reliability indicators of technical systems and ensuring their regulated performance, dependencies were formed to determine the extremum of economic efficiency indicators at a normalized value of the probability of failure-free operation. Based on an analysis of design, production and operation conditions, the parameters of the objective function were determined, including for restored objects. Regulation of reliability indicators was presented as a solution to a multifactor optimization problem. The problem of distributing requirements for the reliability of a complex technical system, consisting of statistically independent indicators of subsystems, was formulated as a conditional optimization problem. In relation to the regulation of reliability indicators and criteria for failures and limit states, factors were grouped according to the characteristics and internal indicators of the object of general classification characteristics, their stratification and ranking. The structure and procedure for preparing initial data was formed.

Use of information redundancy to increase the reliability of devices for storing, processing and transmitting information

In modern information transmission systems, a special place is occupied by telecommunication systems (TS), which include digital data transmission systems (DSTS) containing specialized computers (SEVMs). The systems under consideration must ensure fast and reliable transmission of discrete data over communication lines. In this case, the loss of even one transmitted character is unacceptable; therefore, the main indicator of the reliability of a computer is the probability of failure-free operation. To increase the probability of failure-free operation of a storage device (MS), corrective codes and duplication are used, and to increase the probability of failure-free operation of the arithmetic-logical unit (ALU) of a computer, majority redundancy is used. The disadvantage of the majority method is the high hardware costs for redundancy, which reduces the efficiency of its use. The disadvantages of using correction codes include: as a rule, they are used for separate redundancy (detection and correction of errors that occur in storage devices; majority redundancy is used to detect and correct errors in the ALU); not all arithmetic and logical operations can be controlled based on existing correcting codes; a sharp increase in hardware costs when using algebraic linear codes to detect and correct multiple errors. Detection of errors in the ALU of a computer processor can be achieved on the basis of duplication in a loaded mode with replacement, however, this is associated with solving the main problem of computer duplication: - selection of monitoring tools for determining a failed channel (detection of errors in storage and information processing devices). The purpose of the research is to develop a scientific and methodological apparatus for computer backup using the duplication method with error detection in backup channels based on the use of an algebraic linear code, which makes it possible to detect errors not only in storage devices, but also adapted for detecting errors when performing arithmetic and logical operations. Results. An analysis of operation and selection of reliability indicators for specialized computers (SEVMs) of telecommunication systems was carried out. Requirements for computer backup methods are formulated. A comparative assessment of the detecting ability and hardware costs was carried out when implementing the majority redundancy method, the duplication method and the use of correcting codes. The expediency of using the duplication method is substantiated to increase the probability of failure-free operation and survivability of self-healing digital computers, using algebraic linear codes to determine the faulty channel, which allows to significantly reduce hardware costs for constructing monitoring equipment and use 10-30% of backup equipment for these purposes. It is proposed to use an algebraic linear code, in which, unlike well-known codes, the values of the check bits correspond to the direct and inverse values of the information bits, which makes it possible to detect errors when reading information from the inverse outputs of the memory, correct single errors, detect double errors and control the logical inversion operation , necessary to represent a negative number in two's complement code, which makes it possible to adapt the code to control arithmetic and logical operations of the computer processor. An assessment was made of the probability of failure-free operation of a duplicated computer, with its general redundancy, with detection and correction of single errors in the backup memory channels and detection of errors in the backup channels of the processor ALU based on the proposed code, and an assessment of the probability of failure-free operation of the computer, with its separate redundancy, with error detection in the backup channels of the duplicated memory based on the Hamming code and error correction in the backup channels of the processor ALU based on the majority method. A comparative assessment of the probabilities of failure-free operation allows us to conclude that the general redundancy of the computer based on the proposed code, in comparison with the separate redundancy of the memory and ALU of the computer processor, allows for a gain in the probability of failure-free operation of the computer and its functional devices throughout the entire period of operation. The practical significance lies in the fact that the proposed scientific and methodological apparatus provides: reduction of hardware costs for identifying a faulty channel when organizing duplication; detection of errors in the memory and ALU of the computer processor with time costs not exceeding the time of error detection when using standard methods of monitoring the computer system.

Methods for assessing the reliability of in-shop power supply

Research activities in the field of development of electrical power and electrical equipment include the development of new approaches to assessing the reliability indicators of electrical equipment elements and in-house power supply systems in general. The study has examined methods for assessing the reliability of electrical equipment in intra-shop power supply systems using the example of a workshop network section, including its main elements: power transformer, low-voltage cable lines, distribution points, circuit breakers, magnetic starters, contactors, switches. The reliability parameters of the circuit are calculated relative to the distribution cabinet of the power (DCp) and the distribution point of the power (DPp); regarding each connection of DCp and DPp. The methods under consideration are recommended to be used to clarify the frequency and timing of maintenance and repairs of electrical equipment of the in-shop power supply system, as well as to analyze the reliability of operation and identify the least reliable sections of network diagrams. The presented calculation using the logical-probabilistic method by constructing a fault tree is advisable to use to estimate the frequency of power loss of DCp and DPp, as well as individual connections. For the studied circuits, graphical dependences of the probability of failure-free operation of electrical equipment and the occurrence of a failure over time have been constructed.

Distributed Data Proceeding Systems Architectures Resource Efficiency Improvement on the Basis of Apriory Data about the Jobs Late Completion Times

Purpose of research. The purpose of this study is to develop a method for improving the efficiency of distributed architectures of data processing systems operating in the fog and edge layers of the network. In conditions of high dynamics of both the network infrastructure and the load, the task of forming the architecture of data processing systems is solved regularly (migration of virtual machines, horizontal scalingб etc.) At the same time, the issue of the consumption of the residual resource of computing nodes is practically not considered, while the often used devices have relatively low capacity, and their high workload leads to a reduction in the service life. Therefore, the creation of methods for forming an architecture of a computing device system that is effective in terms of saving a computing resource is an urgent task.Methods. The main scientific methods used in this study are domain analysis, operations research methods, optimization methods and computer modeling, confirming the feasibility of the main aspects of the developed method. To improve the efficiency of placing computational tasks on the nodes of a network fragment, this paper formulated a multicriteria optimization problem, where each element of the vector objective function corresponds to an individual value of the probability of failure-free operation of a computing device. To obtain estimated values of the cost function, a priori estimates of the late completion of the solution of computational problems by nodes are used, since the resource allocated for solving depends on the allocated time, and the time for solving the problem, respectively, on the allocated computing resource. The value of the cost function is calculated on the basis of approximate a priori estimates, which leads to a positive effect in terms of the consumption of computing resources of devices.Results. The result of the study is a developed method for improving the efficiency of distributed architectures of data processing systems operating in the fog and edge layers of the network.Conclusion. The method proposed in this work allows to choose such a load distribution in order to reduce the workload of devices and thus reduce the consumption of computing resources of the devices.

MODERNIZATION OF MOVEABLE CONNECTIONS OF THE SECTION OF THE SOWING COMPLEX

The efficiency of planting seeds and, therefore, the yield of agricultural crops depend significantly on the characteristics of the mechanisms of copying sowing sections. These mechanisms can be conditionally divided into two categories: radial and parallelogram. Radial mechanisms with leashes are used in traditional technologies and require high-quality preliminary processing, and radial mechanisms with pressure rods are suitable for any agrophones The durability of the movable joints of the parallelogram copying mechanism of the sowing complex depends on their resistance to wear. This stability is determined by the mode of operation, chemical composition and structure of the surface layer of parts, as well as physical-mechanical and tribotechnical characteristics. With an average seasonal task for Agro-Soyuz Turbosem II 19-60 sowing complexes within 3–4 thousand hectares, the total service life of experimental parts is at least 4 years, which is at least four times more than in the case of serial parts. The positive effect of the absence (or the presence within the measurement error) of wear of steel parts of movable joints that work in connection with polymer composite material (PCM) was revealed. The average resource of experimental parts in the hinges of the parallelogram copying mechanism for Agro-Soyuz Turbosem II 19-60 seeding complexes is 20589 ha. The average value of the wear of the experimental parts was determined to be 1.78 mm, and the intensity of their wear was 1.02×10-4 mm/ha. It was established that the wear of UPA-6-30 PCM parts in the moving joints of the copying mechanism occurs according to the normal distribution law ( = 0.108), which allows very accurate prediction of their resource. The consistency of the experimental distribution with the theoretical distribution was checked using the Kolmogorov criterion. It is confirmed that the distribution takes place according to the normal law. An analysis of reliability indicators during shortened tests was also carried out and the probability of failure-free operation of experimental parts made of polymer-composite material was determined. According to the results of field tests of the elements of the movable joints of the mechanism of copying the sowing complex, it was established that the resource value of 20,558 hectares exceeds the indicators of serial parts by 4 times.

INCREASING THE RELIABILITY OF ELECTRIC POWER FACILITIES THROUGH THE USE OF UNMANNED AERIAL VEHICLES

The issue of increasing the reliability of the operation of facilities in the energy system of Ukraine is being considered. It is shown that the electric power complex of Ukraine has significant levels of depreciation, which, in turn, leads to an increase in the number of emergency conditions, an increase in the time of post-accident recovery, and as a result, a decrease in the reliability of power supply in general. Accordingly, the loss of electrical energy will be the more, the higher the wear of systems and equipment. Maintenance costs must also increase to keep the power system within regulatory requirements for high wear equipment. Outdated and worn-out equipment leads to an increase in energy losses, an increase in the cost of maintaining the state of working capacity and, as a result, financial losses. Reduction of electricity losses on worn-out equipment cannot be carried out instantly and radically due to the impossibility of the Ukrainian economy to upgrade power equipment in a short time. The authors propose to reduce financial losses by reducing the cost of maintaining existing equipment. And it is proposed to do this through the use of modern technologies, namely the use of UAVs for monitoring power equipment. It is proposed to pay attention to only one parameter, namely the uninterrupted operation of power facilities. Thus, for network companies monitoring the technical condition of lines and control of isolation means is the main type of monitoring. Density of failures of equipment operation is built in graphical form, where a normalized number of inspections is presented, based on reliability requirements. The number of inspections is calculated according to regulatory documents. The paper shows that the graph of the change in the probability of failure-free operation is not straight. Therefore, the frequency of inspections cannot use the frequency that is not related to the wear and tear of the equipment. And to maintain the level of reliability, it is necessary to increase the number of inspections to ensure the standard level of reliability. Therefore, the authors propose to reduce costs with an increased number of inspections using UAVs. The above economic calculations show the high economic efficiency of such a proposal.

Evaluation of the effectiveness of sliding redundancy of radioelectronic facilities

Objectives. The increased reliability of radioelectronic facilities can be achieved by the application of structural and load redundancy. Structural redundancy is achieved taking into account multiplicity of redundancy and the intensity of failures of elements of radioelectronic facilities, while load redundancy involves an easing of electrical, thermal, and mechanical operating modes of the elements. The choice of a redundancy method is determined according to reliability indicator requirements, which may often be contradictory. Therefore, the problem of how to effectively combine structural redundancy and load redundancy methods is very topical. In long-life radioelectronic facilities, for example, in satellite communication repeater systems, sliding redundancy is applied when limiting mass-dimensional parameters and consequently consumed energy. The aim of the work is to evaluate the efficiency of sliding redundancy according to various reliability indicators when altering redundancy multiplicity, reserve operating mode, element failure intensity, and switching device type.Methods. To describe the structure of a complex sliding redundancy system, a logical-probabilistic method is used, in which the dependence of the system reliability indicators on the reliability indicators of the elements is formulated as a logical function of operability. Graph-analytical methods are used to compare different variants of reliability logic schemes.Results. Mathematical models have been obtained to evaluate the effectiveness of sliding reservation. A comparative analysis of the efficiency of sliding redundancy with a loaded and unloaded reserve was carried out in terms failure-free operation probability, as well as gamma-percentage resource, failure rate when changing the fractional multiplicity of the redundancy, and element failure rate. The influence of the reliability of the switching device on the efficiency of the sliding redundancy is considered.Conclusions. Practical recommendations on the selection of the redundancy mode are presented according to different reliability indices and constructed mathematical models of the sliding redundancy efficiency coefficients. The correlation between the reliability indices of elements and the switching device whose reliability can be discounted, is determined. To increase the efficiency of sliding redundancy of radioelectronic facilities, it is necessary to combine multiplicity of redundancy and the operating mode of the reserve with approaches aimed at reducing the intensity of failure of elements.

Study of the regularity of wear influence on the service life of cutting elements of bulldozers’ working bodies

Our mathematical model describes the regularities of blade wear and takes into account the influence of different operating modes of a bulldozer when dealing with diverse soils that have different degrees of abrasiveness. When calculating the probability of failure-free operation of the bulldozer cutting elements (blades), which depends on the maximum load, it was found that the probability of failure-free operation at an operating time of 600 machine-hours is 0.7...0.75 – for soil category I; 0.5...0.55 – for soil category II; 0.3...0.35 – for soil category III. Comparison of failure-free operation probabilities has made it possible to establish that with an increase in soil density, failure-free operation probability drops by 30-40%, which suggests a significant impact of soil density on reliability of the bulldozer working equipment. In addition, this mathematical model of the total probability allows us to obtain a theoretical description of changes in failure-free operation probability of the bulldozer equipment during working processes, changes in the service life of a bulldozer blade, and taking into account the properties of the blade material. The service life of a bulldozer cutting element can be estimated by its wear, structural features of the material, geometric parameters (thickness in particular), and machine operating modes. It has been established that the regularity of changes in the service life, due to bulldozer blade wear, is exponential. The higher the soil category is, the lower the wear is, and hence the service life of a bulldozer working body. The dependence of the change in the blade service life on the time of its contact with soils of three categories was obtained as well. Thus, the maximum value of a blade service life at the beginning of operation on different soil categories was determined: 450 machine-hours – on soil category I; 350 machine-hours – on soil category II; 280 machine-hours – on soil category III.

Mathematical Analysis of the Reliability of Modern Trolleybuses and Electric Buses

The rhythmic and stable operation of trolleybuses and autonomous trolleybuses or urban electric buses, depends to a large extent on the reliability of the equipment installed on the trolleybus. The actual operational reliability of trolleybus electrical equipment (EE) depends on its technical condition. Under the influence of external factors and specific operating modes, the technical condition of the equipment is continuously deteriorating, reliability indicators are decreasing, and the number of failures is increasing. Using the mathematical theory of reliability, probability theory and mathematical statistics, numerical methods of solving nonlinear and transcendental equations, this article defines the conditions of diagnostics depending on the intensity of failures and the given probability of failure-free operation of the equipment. Additionally, the inverse problem of determining the current reliability of electrical engineering systems depends on the terms of diagnostics and the intensity of failures being solved. As a result of the processing of statistical information on failures it is established that for the electrical equipment of a trolleybus, after a number of repair measures, the maximum density of failures occurs at a lower mileage, and the probability of failure-free operation can vary depending on the degree of wear of the equipment, i.e., on the number of previous failures. It is theoretically substantiated and experimentally confirmed that the reliability of trolleybus electrical equipment changes according to the exponential law of distribution of a random variable. It has been established that the real averaged diagnostic terms regulated by instructions are not optimal in most cases and differ several times from those defined in this paper. The dependence of switching equipment run-in on time has been clarified, which served as a prerequisite for specifying the inter-repair period for various types of trolleybus electrical equipment. A method of adjustment of the inter-repair time for the electrical equipment of trolleybuses is proposed.

Methodical bases of processing the results of research on guided and unguided missiles solid fuel engines

In the article is given methodical approach of determining and confirming of main traction force characteristics of different purpose missiles solid fuel engines. The probability of failure-free operation at the define functionality time is proposed as basis reliability rate, which is calculated with taking into account the structural functional scheme of solid fuel engines which are under research. This approach allows to taking into account the construction peculiarities of engines components parts and elements and interconnection between them. In the article also given interconnection between speed of guided missiles at the end of active flying trajectory and traction force impulse of their solid fuel engines which are defining from tests results.

A METHOD OF PREDICTING FAILURE RATES OF AN UNMANNED AIRCRAFT COMPLEX BASED ON CONTROLLED OPERATION DATA

The article provides a description of the method for determining the fault-free work indicators (FWI) of unmanned aerial systems (UAS) during their controlled exploitation (CE). It is noted that’s standard approaches to determining the reliability indicators operate with idealized models of situations in which the number of failures is calculated by various ways, and then statistical models are built on this basis. Further, taking in to account various assumptions of the author, reliability indicators are formulated, and, as their subsets, FWI as well.
 Thus, there is a situation of a contradiction between the “noisy” experimental model data and the ultimate UAS FWI (number of failures, MTBF, failure rate and probability of failure-free operation), which are formulated by analogy with their idealized prototypes.
 It is proposed to overcome this contradiction by developing a method that would calculate the number of UAS failures N* during the standard СE period (conventionally 100 flights), the average integral MTBF T* in the CE period of UAS, the average integrated failure rate λ* in the CE period of UAS, and the average integral probability P* in the CE period of UAS.
 The determination of the devalues is proposed to be carried out on the basis of data obtained during the controlled UAS exploitation, according to the method described in this article here by.
 Monitoring the progress of the controlled UAS exploitation is carried out by documenting the facts concerning failures and updates using the Dynamic Bayesian Trust Network (DBN). By the CE beginning, DBN is created using the Bayes Fusion GeNiE Academic 2.5 simulation environment.
 The tracking process is implemented by making to the DBN records (evidences) about the failure and restoration of the complex in the CE process. These significations are inputting into the model the information about whether at a certain point of time a certain UAS element failed or it was restored after the failure. This information is the result of the UAS observation, and in DBN this causes an immediate recalculation of conditional posterior probabilities of failure-free operation of all whose operability depends on the operability of the nodes got evidenced. This information appears in the actions flow of the practical use of the BPAC and is transmitted to the flow of documenting failures that the operator performs in the DBN. These actions enable the external, relatively DBN, software to calculate the ultimate UAS FWI.

Methodology for Calculating Indicators of Reliability of Power Supply, Taking Into Account Seasonality

It was revealed that emergency and planned outages in electrical networks are seasonal in nature by months of the year and time of day. Information about the methods for calculating the indicators of reliability of power supply to rural consumers is given and their analysis is performed. It is shown that the existing methods do not allow for a differentiated calculation of reliability indicators depending on the season of the year and the time of day. A methodology has been developed for calculating these indicators, taking into account seasonality by months and time of day, which makes it possible to obtain the probability of failure-free operation for emergency and planned outages, taking into account the corresponding seasonality coefficients.

THE STRUCTURE OF THE COMPUTER SYSTEM IN THE RESIDUAL CLASSES

The subject of the article is the formulation and solution of the inverse problem of optimal redundancy in the system of residual classes (RNS) based on the use of the dynamic programming method. The solution of this problem makes it possible to improve the reliability of the operation of computer systems and components (CSC) in the RNS. The purpose of the article is to increase the reliability of the functioning of CSC, which are built on the basis of the use of RNS, without reducing the speed of calculations, as well as to calculate and compare the reliability, in terms of the probability of failure-free operation, of CSC in RNS and a tripled computing system that operates in a positional binary number system (PNS). Tasks: to analyze the influence of the number system used on the reliability of the CSC, taking into account the primary and secondary redundancy; to synthesize a computing system in RNS for a l-byte bit grid based on the use of the passive fault tolerance method (constant structural redundancy); formulate and solve the inverse problem of optimal redundancy in RNS based on the use of the dynamic programming method; to check the correctness of the results obtained, calculate the conditional amount of computer system equipment in the residual classes; evaluate the efficiency of using RNS to improve reliability when building a redundant CSC in relation to a redundant CSC in the PNS. Research methods: methods of analysis and synthesis of computer systems, number theory, coding theory in RNS, reliability theory. The following results are obtained. The paper shows that the use of PNS as a number system does not allow a radical increase in the performance and reliability of CSC. In this regard, the article developed the concept of using RNS as a number system for constructing a CSC. Based on this, the inverse problem of optimal redundancy in RNS is formulated and solved. Conclusions. As shown by the results of calculations and comparative analysis, the use of RNS provides a higher reliability of the CSC than the majority three-channel computing system in the PNS. The obtained research results can be used for the synthesis of fault-tolerant computer structures in RNS.

Production Facilities Safety Assessment According to the Maximum Values of Machines Reliability

Introduction. At the stage of designing technical devices and performing appropriate strength calculations of metal structures, sufficiently large reserves of strength are taken, which, theoretically, exclude any failures of parts. In fact, the machines work with frequent failures. Of interest are undiagnosed failures that lead to a critical decrease in safety, especially at hazardous production facilities. It is assumed that the previously applied approaches of selective determination of the maximum (minimum) reliability value, based on point estimates of the distribution parameters of the two-parameter Weibull law, lead to an overestimation of the calculated indicators of the probability of failure-free operation, i.e. underestimation of risk. Therefore, the work objective is to consider an approach to assessing the risk of operating production facilities in a situation of accidental occurrence of dangerous and undiagnosed failures in systems.Materials and Methods. Methods for technical devices safety assessment based on probability theory were used in the work, and the probability of machine failure was determined based on the well-known method of reliability theory. This method consists in calculating and constructing distribution functions of random variables (load-bearing capacity and loading) that influence the occurrence of failure. The level of increase in the reliability index was determined, leading to frequent unpredictable failures of technical devices (machines) and a decrease in the safety of their operation.Results. The signs of inconsistency of strength calculations based on overestimated safety margins, which in theory exclude failures of parts and machines in general, are identified and substantiated. A new approach to risk assessment of operating production facilities in a situation of accidental occurrence of dangerous and undiagnosed failures by safety systems has been developed and implemented. An algorithm for determining the three parameters of Weibull's law for a population based on sample data has been developed. The resource distribution densities of the boom of the single-bucket excavator EK-14 are constructed. The recommendations are given to increase the probability of failure-free operation to 0.9989.Discussion and Conclusion. The results of the conducted research allow us to substantiate a new approach to risk assessment of operating production facilities in the event of dangerous and undiagnosed failures of basic parts by safety systems, leading to negative consequences.

METHODOLOGICAL AND TECHNOLOGICAL BASICS OF RESEARCH OF SOLID FUEL ROCKET ENGINES OF ATTACK MEANS

The article presents methodical and technological approaches to the study of performance and confirming the main characteristics of solid fuel rocket engines (SFRI), which are part of various means of destruction, as well as the main directions of organization and features of the relevant fire bench tests.
 SFRI is one of the most important components of modern means of destruction, which largely determine their tactical and technical characteristics and operational safety. By their technical condition, we mean a set of properties that change during operation and are characterized by the parameters (signs) defined by technical documentation.
 A structural-functional reliability scheme is developed to assess the reliability of SFRI, which allows taking into account not only the structural elements, but also phenomena that can lead to failures, including those caused by connections between elements. According to the results of bench fire tests of SFRI that are conducted taking into account the structural-functional reliability scheme, the following information is obtained: internal ballistic, mass, energy and traction characteristics; performance of structural elements and nodes; characteristics of operational reliability and control bodies. At the end of the tests, the remaining thickness of the heat shield, the integrity of the SFRI body and the condition of the exit nozzle are also evaluated. The probability of failure-free operation is used as the main indicator of reliability. As the main indicator of reliability, SFRI uses the probability of failure-free operation for a given time of its operation. The reliability indicators of individual components are determined in accordance with its structural and functional reliability scheme.
 Fire stand tests of SFRI are carried out on a special stand, which includes original technological equipment developed and manufactured at the State Enterprise “Kyiv State Design Bureau “Luch”, the main of which are: equipment for remote launch of marching and starting АЗСД 7Х2.700.017; equipment for remote measurement and registration of operating parameters АИР 7X2.700.016; slipway С–40T–1 E240.125.00.000.0 with sensors and a sensor for registering internal gas pressure.
 The implementation of the main provisions of the methodological and technological basis of SFRI research made it possible to make scientifically based decisions regarding the possibility and expediency of their further exploitation, as well as the need to introduce a number of restrictions, including decommissioning.

Forecasting the technical condition of thermochemical reactor systems

Today, thermochemical reactors are an integral element in many industries. Failure of reactor elements can lead to significant negative consequences. An analysis of the consequences of failures of thermochemical reactors containing a stirrer is presented. The FMEA method has been used to determine the main causes of failures in thermochemical reactors with agitator. When using failure statistics, the Pareto chart shows the distribution of the main causes of agitator failure. It has been established that the combination of the most significant causes leads to the failure of the bearing units and, as a result, the mixing device. A Markov model of the failure rate of bearing assemblies of a thermochemical reactor using rolling bearings, as well as magnetostatic bearings, is presented. Using the method of Markov processes, the rationale for replacing the rolling bearings of a mixing device with magnetostatic bearing assemblies is shown. The probability of failure-free operation as a result of calculations was 0.9998 for bearings based on rolling bearings and 0.9999 for magnetostatic bearings. Keywords: failure analysis; thermochemical reactor; Markov processes; mixing device; bearing assembly; technical condition.

Probably-based stock coefficient as an optimization criterion in the design of agricultural equipment

The publication aims to introduce the production process of manufacturing elements of technical systems of analytical models for ensuring the reliability of equipment at the design stage, considering the experience of operating previous systems or their analogs. The proposed method of determining the main optimization criteria is used in the example of agricultural tillage machines. A representative statistical analysis of operational information on the reliability of soil tillage units, which have oscillating movement of working bodies, was performed. The work results under the operation conditions of thirteen cultivators with a total yield of more than 280 thousand ha was considered. Functional studies were conducted in 7 regions of Ukraine. In addition, they are characterized by various soil and climatic conditions. The occurrence of sudden failures due to the breakage of the adjustable racks of the working bodies of the cultivators has been established. Forty-two premature failures were recorded among the 260 racks that were tested. The paper proposes an inversion method that allows determining the load parameters of elastic elements, the concept of which is a combination of the capabilities of the theoretical model of reliability, which is adapted to forecasting the probability of failure-free operation due to sudden failures with specific indicators of the statistical model, which are obtained depending on the performance of adjustable racks. The given approach provides an opportunity to determine the impact of the load on existing machine designs and their elements, which lead to sudden failures based on evaluating the operation of tillage units. It is possible to present such an influence in the form of a probabilistically justified reserve factor, which has an empirical basis and makes it possible to correct the theoretically assumed load value during the design of the next generation of technical systems and their elements. Constructive and technological changes during the procedure, based on the approach described in the article, provide an opportunity to manage the level of reliability for economic and image reasons. Keywords: inversion method, elastic element, extreme load, probability of failure-free operation, reserve factor, reliability, design.

Analysis of the effectiveness of methods for ensuring the reliability of a communication satellite transponder

Objectives . Since the launch of satellite communication systems in practical use, approaches towards enhancing their operational quality and durability have been developing in the direction of increased reliability of airborne transponders. This is mainly achieved by increasing redundancy and using components with a lower failure rate. In this regard, the creation of new technologies and new materials is a particularly promising direction. However, since durability testing of complex systems can take several years, the problem of ensuring an effective combination of redundancy methods and elements having a reduced failure rate remains challenging. The purpose of the work is to analyze the effectiveness of methods for ensuring the reliability of a communication satellite transponder based on a proposed methodology for determining the durability index using a mathematical model of the probability of failure-free operation. Methods . In order to describe the complex structure of a satellite communication system transponder, a logical- probabilistic method is used, in which the dependence of the system reliability indicators on the reliability indicators of the transponder elements is formulated as a logical function of operability. Mathematical models of system reliability are created on this basis including for redundant systems. Graphs and analytical methods are used to compare different systems. Results . The influence of various methods for ensuring the redundancy of transponder devices and the use of more reliable components on the reliability and durability indicators is considered. A gamma-percentage resource-based technique for determining the durability indicator based on the constructed mathematical models of the probability of failure-free operation is presented along with a comparative analysis of measures to increase the gamma-percentage resource of the transponder. Conclusions . The presented method for determining the durability index using a mathematical model of the probability of no-failure operation can be used to determine the time interval within which redundancy increases the probability of no-failure operation as compared with a decrease in the failure rate of elements. On this basis, the most effective combination of redundancy methods and approaches for reducing the failure rate of elements can be identified.